Insulation

Q&A: Is Housewrap Needed?

Air Barrier Basics

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A.Wood siding can be nailed directly over plywood sheathing without a house wrap, rosin paper, or building felt, but I would not recommend it.

Primarily, an exterior air barrier, whether it is a plastic housewrap, rosin paper, or asphalt impregnated felt, prevents air infiltration through cracks in the building shell that aren’t usually sealed, such as the joints between the plate and the subfloor, around the band joist, and between the sheathing. If all the joints in the sheathing are...